This invention generally relates to devices for performing endoscopic medical procedures. More specifically, this invention relates to devices for ligating and cutting body vessels. When performing medical procedures it is often necessary to ligate, or block the flow of, by crimping, a body vessel such as a vein or artery. It may also be necessary to cut the vessel. In endoscopic procedures the surgical treatment occurs at a distance, through a small incision in the patient's skin. In these procedures cutting and ligating vessels generally requires specialized instrumentation inserted through the incision. Even with such instrumentation these functions can be challenging.
When grasping a vessel in preparation of other procedures it is important to obtain a secure grip on the vessel. It is also important to avoid dislodging the vessel from its normal position. Vessels which are not securely grasped are difficult to ligate and cut. Vessels which are dislodged from their normal position may spring back or recede from their new position once the procedure has been completed. Additionally, vessels which are dislodged may avulse, or damage connecting main branches, or in other words, moving a tributary may damage a saphenous vein. Loosely grasped vessels unduly complicate the medical procedure. Furthermore, after cutting a vessel in two or more places, a securely grasped vessel can be "harvested" by withdrawing the instrument and the grasped vessel.
Many current devices grasp body vessels by sliding over them in an effort to trap them within the instrument. This procedure produces an insecurely grasped vessel, due to the one-way trapping employed. This procedure also presents an uncertainty as to whether the vessel is adequately trapped within the instrument. Furthermore, these devices tend to dislodge the vessel from its normal position in an effort to trap the vessel. This is especially so for minimally invasive devices which are often very long. The normal movement of the operators hands is multiplied by the length of the device, so distal tip manipulation is difficult to control.
When ligating a vessel it is important to completely and securely cut off the flow of the vessel. The clips used for ligation need to maintain a sufficient compression on the vessel to stop flow within the vessel and to remain secured on the vessel. Clips which leak or become dislodged from the vessel unduly complicate the medical procedure.
Current devices use several different methods of ligating a body vessel. One method uses a closed clip construction of a particular configuration, which requires the clip to be mechanically bent open by an applicator to advance the clip over the body vessel. This requires the clip to be flexible enough so that bending the clip open will not permanently deform the clip more than is necessary to apply the clip. A more flexible clip will most likely be larger in size or have lower retention force to the vessel it is applied to.
Another method uses an open clip construction, which requires the clip to be crimped after advancing the clip over the body vessel. This requires the medical device to provide sufficient force to permanently deform the clip over the body vessel. As in the first method, this requires the clip to be formed of relatively flexible material. Regardless of the material used, the permanent deformation during crimping can compromise compression strength by reducing the spring forces in the clip. Open clips take up more space and thus require larger delivery systems. Creating the great force necessary to close clips tends to be quite complex when it must be done in a small, disposable delivery system. Closed clips require much less force to apply, are easier to apply (because the force is applied along the length of the device and not perpendicular to it), and have tighter dimensional control in their applied state because they are closed in a manufacturing environment with clip forming machinery.
When cutting body vessels it is important to maintain a consistent cutting force so that the cut edges of the vessel are even and consistent. Inconsistent or uneven edges may be difficult to later re-attach or permanently close. Current devices use a scissoring method with a hinged lever-type action to cut a vessel. Such a method produces a cutting force which varies with the distance from the hinge point. Variations in cutting force varies the cutting efficiency and may produce uneven edges or an incomplete cut.
Since many different procedures exist which require endoscopic ligating and cutting of vessels it is necessary that the device be capable of variable and multiple functions within a single procedure. Such operating flexibility has been difficult to achieve in a simple, easy to use device. The complexity of endoscopic surgery requires that the instrumentation be easily manageable. A simple hand-held device with a minimum of control mechanisms is preferrable to more complex designs.
One of the great difficulties associated with minimally invasive surgery is the time required to change out the surgical tools. Minimally invasive surgery is typically performed through a small number of "ports" that are often not near to the targeted surgical region. This limits the number of devices allowable and hinders the locating of the business ends of the devices at the surgical region. Multi-function devices help in this regard.
What has been needed and heretofore unavailable is an endoscopic instrument which is capable of efficiently ligating and cutting a body vessel and having sufficient operating flexibility to be used in various procedures. Furthermore, a ligating clip has been needed which completely and reliably stops the flow through a body vessel during surgery. The present invention satisfies these needs.